A time domain multiple access (TDMA) satellite communications controller, such as that described by Alvarez, et al. in the copending U.S. patent application entitled "Time Domain Multiple Access Broadcasting, Multipoint and Conferencing Communication Apparatus and Method," Ser. No. 130,498, filed Mar. 14, 1980, assigned to the instant assignee, and incorporated herein by reference, has a format which can be seen in FIG. 1. A TDMA frame is 15 milliseconds long, consisting of a control field and a traffic field. The traffic field contains approximately 1400 channels, each headed by a destination address field of 32 bits followed by a data field of 480 bits. There are 20 TDMA frames in a superframe group. The destination address specifies the destination satellite communications controller (SCC) and the address in the receive burst buffer (RBB) used by the destination SCC to store the data being transmitted. When transmitting encrypted data, a problem arises in such a TDMA system in coordinating the encryption and decryption engines in the respective earth stations since there is typically a 300 millisecond delay between the transmission of the encrypted data from a transmitting station and the reception and decryption of that data at a receiving station. Some means must be provided to coordinate the encryption and decryption engines and still further, to enable a channel of information to be decrypted at any time within a TDMA frame.